BANGKOK — Searchers in Thailand have recovered 18 bodies and are continuing to look for at least 12 people missing from a heavily loaded boat that sank in a river over the weekend, officials said.

The two-deck boat was carrying more than 100 Muslims on a holiday excursion when it sank Sunday afternoon on the Chao Phraya river 80 kilometers (50 miles) north of Bangkok. The boat evidently ran up in shallows then took on water, sinking in less than two minutes just a few meters from the riverbank.

The upper deck — its open railings brightly painting in red with white trim — remained visible above the muddy water as rescuers worked to stabilize the boat to be searched.

Bodies were still being retrieved Monday afternoon, with 18 recovered so far, a Marine Department official said, speaking on condition of anonymity because she was not authorized to release information. Some bodies were found in the boat, while others had drifted downstream.

In addition to the dead and missing, 44 people were injured. Twelve people are unaccounted for, though others may still be missing.

A Harbor Department official, Surasak Sansombat, was quoted earlier by ThaiPBS television as saying that the boat’s listed capacity was 50 passengers and it probably sank from overloading.

“Many passengers tried to jump out of the boat and scrambled toward the shore, which was about three to five meters away,” Annop Kudeephan, a 50-year-old survivor, was quoted as saying in The Nation newspaper.